Re: alfa-digest V7 #629

[CaptWSims@domain.elided]

In a message dated 4/9/99 8:50:06 PM Eastern Daylight Time, 
owner-alfa-digest@domain.elided writes:

<< 2. Getting down to the actual meat of the matter: If
 you're REALLY going to balance an engine, you can't
 dismiss ANY significant rotating or reciprocating
 mass, can you? And "half-speed" at 7500 rpm is still
 3750, which ain't exactly poking along.  >>

I just joined the digest, so I hope I'm not beating a dead horse....I'd like 
to add my 2 cents to the balancing debate.  When I built the 2 liter for my 
'78 Sprint Veloce a few years ago I was shooting for 160-170 hp in a 
streetable car that would be used sometimes on the road, mostly driving to 
autocross events.  One of my resources was a book written by "Smoky Yunick".  
He was in his prime racing back in the 60s (I saw him run back then), but his 
book on building engines was of interest.  He contended that when balancing 
an engine one should worry very much about any reciprocating mass and ignore 
any rotating mass.  He claimed that dynamic balancing of crankshafts didn't 
hurt but didn't help because there is a rope of oil wrapping around the crank 
at high rpm, and this rope of oil is constantly changing in mass and 
location.  

When building my engine I balanced the pistons and the small ends of the 
connecting rods only (per his recommendation) and spent a day getting them 
all within 3 grains.  (yeah, grains, not grams).  The engine is silky smooth 
to the redline of 7000.  I'd do it the same way again.   

										
			Bill Sims
										
			Virginia Beach  

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